Onix was first seen during Brock's match with Ash at the Pewter Gym where it was used against Pikachu. Onix wasn't fazed by Pikachu's Thunder Shocks because of its secondary Ground type, and was easily able to subdue Pikachu with a Bind. Ash decided to forfeit the match because he couldn't stand to see Pikachu in pain. Onix was also used in Brock's rematch with Ash where it battled Pikachu once again. This time Pikachu's newly learned Thunderbolt attack was actually able to cause damage to Onix, though it was still not enough to defeat it. Onix once again had Pikachu in a Bind until Brock told it to stop because Brock didn't want to hurt Pikachu. Eventually Pikachu's Thunderbolt set off the sprinklers, severely damaging Onix because of its severe weakness to water. Pikachu took Onix down with one final Thunderbolt, but Ash chose to forfeit. Brock decided to give Ash the Boulder Badge anyway, and then joined him on his journey, bringing Onix with him.

Forming a staircase to help Ash and Brock escape

Like most of Brock's Pokémon, Onix received very little screentime in comparison to the Pokémon of the other main characters. This may have been due to its massive size, although this came in handy when the trio were trapped in the upside down, sunken St. Anne in Pokémon Shipwreck. Onix was used as a bridge and ladder to allow the group to reach lower levels of the ship.

Onix and Brock in the race

Onix was sent out in an attempt to prevent Team Rocket escaping with a Moon Stone in Clefairy and the Moon Stone. It tunneled through ground and burst up to disrupt the escaping Team Rocket, and although it fought to a stalemate with Koffing, it held them up long enough for Ash and the others to arrive and save the day.

Onix was used as Brock's steed in The Flame Pokémon-athon!, during the big race. It managed to maintain second behind Dario and just ahead of a farmhand on a Rhyhorn. However, the race involved crossing a body of water, which the two Rock-type Pokémon were unable to cross, and Onix had to withdraw. Onix was noticeably upset by this, the only time it has been shown to weep.

In Who Gets To Keep Togepi?, Brock used Onix in the four-way tournament, where it went up against Meowth. It seemed to outclass the tiny Normal-type Pokémon with Rock Throw, but Meowth was extremely determined after seeing Togepi, and managed to defeat Onix by splashing it with a watering can and then using Fury Swipes.

Johto

Onix swatting Ash and Misty aside trying to dodge Totodile

In Sick Daze, it was revealed that Brock usually polished his Geodude and Onix as part of his Breeder duties. The dubious task of polishing Brock's Onix fell to Ash, who attempted to shorten his chore through use of his Totodile's Water Gun, which caused Onix to panic and earned Ash a reprimand from Misty. It was captured by Team Rocket, but was rescued by the arrival of Brock, Golbat and Pineco. It then used Rock Throw to send Team Rocket blasting off.

In Control Freak!, Jessie, in possession of an ancient Queen's mask and scepter, took control of Onix, along with Geodude and Pikachu. Team Rocket then beat a hasty retreat by ordering Onix to carry them out of the underground chambers. When Team Rocket fled, Onix was freed from the influence of the scepter. In Entei At Your Own Risk, Onix comically buried Psyduck in hot sand as it collapsed in the bed to relax. It later used its large, dense body to shield the group from Team Rocket's suction.

Advanced Generation series

Hoenn

Brock ended up lending Onix and two of his other Pokémon to his eldest sibling, Forrest, who took on the role of Gym Leader at Pewter City while Brock went to Hoenn.

Kanto Battle Frontier

When Brock returned to the Gym in Grating Spaces, Onix had evolved into a Steelix under Forrest's care. Steelix was shown to have learned Iron Tail and a powerful Dragon Breath attack during its time at the Gym. It was used in a Double Battle with Ash and his Donphan against Jessie, James and their newly obtained Charizard and Aggron. The battle started out rough with Steelix being hit by Charizard's powerful Flamethrower. Donphan saved Steelix by attacking Charizard but was pushed back by Aggron's Mega Punch and Hyper Beam. Donphan continued to attack Charizard but was hit hard with Aggron's Water Pulse. Steelix then countered another Flamethrower with an Iron Tail and launched Donphan into the air over Aggron's Water Pulse. Donphan used the momentum to land a devastating Take Down attack on Aggron. The battle was stopped after Forrest discovered it was Team Rocket they were battling.

Diamond & Pearl series

Steelix made an appearance in SS025, in which it was called out by Forrest to have a Gym battle against Nurse Joy. However, at the time Nurse Joy refused to battle anyone but Brock or Flint.

Personality and characteristics

Brock and his Steelix

Like all of Brock's Pokémon, Onix received very little personality development while it was on-screen, which was not often, most likely due to its size. However, it is very loyal to Brock as his starter Pokémon and reflects his personality quite closely. Like Brock, Onix was very intimidating and serious in its debut appearance, mercilessly crushing Pikachu in obedience to its commands. Like Brock, its tough exterior hides a sensitive interior. Just as Brock gets emotional over women, Onix has been shown to be morbidly afraid of water. In the big race in The Flame Pokémon-athon!, Onix kept up a top three position until they hit a body of water and were forced to retire, causing it to cry in disappointment. When necessity forced it to expose itself to water when damming the Cinnabar volcano, it only permitted the tip of its tail to be soaked.

As a Steelix, its personality remains much the same. It was very happy to see Brock again and battled loyally alongside him.

Moves used

This section is incomplete.Please feel free to edit this section to add missing information and complete it. Reason: Sandstorm and Slam image.

A † shows that the move was used recently, unless all moves fit this case or there are fewer than five known moves.

In Pokémon Origins

Brock's Onix in Pokémon Origins

Onix was the second Pokémon Brock used during his Gym battle against Red in the Pokémon Origins episode File 1 - Red. At first, it took massive and almost fatal damage from Red's Nidoran♂'s Double Kick, but was then able to defeat it with Bide. It then proceeded in defeating also Red's Spearow, Rattata, and Metapod in a quick succession, although the last managed to land a String Shot on it before being defeated. Red was left with only Charmander, and as it had also been significantly weakened while battling Brock's Geodude, both Trainers knew that the first one to land a hit on the opponent would win. Thanks to Onix's speed having been reduced by Metapod's String Shot, Charmander was able to outspeed the Rock Snake Pokémon and strike it with Scratch, defeating it and giving Red the victory.

Moves used

A † shows that the move was used recently, unless all moves fit this case or there are fewer than five known moves.

In the Pokémon Adventures manga

Onix in Pokémon Adventures

Red challenges Brock's Onix during Onix is On! in a Gym battle to gain the Boulder Badge. Red uses Pika to battle (his other two partyPokémon too tired from repeated use), but it is still angry with Red for capturing it, and ignored his commands. Onix first uses Rock Throw at Pika, which caused it to become even more annoyed, and it started shocking Red instead. Brock is infuriated that the one challenger he'd hoped to go all-out on seemed to have won his way through "dumb luck." He then revealed Onix's strongest move: using its body like a torpedo to gain momentum and hit Pika with Skull Bash. Red narrowly pushes Pika out of the way, and having decided to fight for him, the Pikachu uses a powerful electric attack on Onix, breaking apart the rocks that its body is composed of. In the end, Red seemed to have gotten Pika's trust, before using the handshake he offered to electrocute him in the outskirts of Pewter City.

In the Pocket Monsters HGSS Jou's Big Adventure manga

In the Pokémon Pocket Monsters manga

Onix in Pokémon Pocket Monsters

Brock's Onix appears in Bring Down the Powerful Opponent Onix!!, in Red's battle with Brock. After witnessing Green and his Charmander being tossed out of the Gym, Clefairy was initially too afraid to face Onix in battle and had attempted to flee, but later gained courage to fight after learning that his cousin Pikachu was part of Brock's collection, which infuriated Clefairy. During the battle, Clefairy tried to use an assortment of tricks to win the battle, which only prolonged the fight. Eventually Clefairy leads Onix around a ceiling column, trapping Onix as it becomes entangled around it. Onix manages to free itself and attempts to crush Clefairy by wrapping its tail around him, but stops after Clefairy cunningly draws his picture onto Onix's tail, which confuses Onix and causes it to chase after its own tail. This makes Onix dizzy, and Clefairy knocks it out by smashing the fallen pillar onto its head, thus winning the battle.

In the TCG

Related cardsCards listed with a blue background are only legal to use in the current Expanded format.Cards listed with a silver background are legal to use in both the current Standard and Expanded formats.